Planet Mercury: Facts About the Planet Closest to the Sun Planet Mercury: Facts About the Planet Closest to the Sun By Charles Q. Choi, Space.com Contributor | November 30, 2016 08:44pm ET MORE This view is one of the first from the MESSENGER probe's Oct. 6, 2008 flyby of Mercury. Credit: NASA/JHUAPL/CIW Mercury is the closest planet to the sun. As such, it circles the sun faster than all the other planets, which is why Romans named it after their swift-footed messenger god. The Sumerians also knew of Mercury since at least 5,000 years ago. It was often associated with Nabu, the god of writing . Mercury was also given separate names for its appearance as both a morning star and as an evening star. Greek astronomers knew, however, that the two names referred to the same body. Heraclitus believed that both Mercury and Venus orbited the sun, not Earth.

[ Latest Photos: Mercury Seen by NASA's Messenger Probe ] Mercury's physical characteristics Because the planet is so close to the sun, Mercury's surface temperature can reach a scorching 840 degrees Fahrenheit (450 degrees Celsius). However, since this world doesn't have a real atmosphere to entrap any heat, at night temperatures can plummet to minus 275 F (minus 170 C), a temperature swing of more than 1,100 degrees F (600 degree C), the greatest in the solar system. Mercury is the smallest planet — it is only slightly larger than Earth's moon. Since it has no significant atmosphere to stop impacts, the planet is pockmarked with craters. About 4 billion years ago, an asteroid roughly 60 miles (100 kilometers) wide struck Mercury with an impact equal to 1 trillion 1-megaton bombs, creating a vast impact crater roughly 960 miles (1,550 km) wide. Known as the Caloris Basin, this crater could hold the entire state of Texas. Another large impact may have helped create the planet's odd spin .

As close to the sun as Mercury is, in 2012, NASA's MESSENGER spacecraft discovered water ice in the craters around its north pole, where regions may be permanently shaded from the heat of the sun. The southern pole may also contain icy pockets, but MESSENGER's orbit did not allowed scientists to probe the area. Comets or meteorites may have delivered ice there, or water vapor may have outgassed from the planet's interior and frozen out at the poles. [Related: First Photos of Water Ice on Mercury Captured by NASA Spacecraft ] As if Mercury isn't small enough, it not only shrank in its past but is continuing to shrink today . The tiny planet is made up of a single continental plate over a cooling iron core. As the core cools, it solidifies, reducing the planet's volume and causing it to shrink. The process crumpled the surface, creating lobe-shaped scarps or cliffs, some hundreds of miles long and soaring up to a mile high. In the past, the surface was constantly reshaped by volcanic activity , some fairly recently in the planet's past.

"The young age of the small scarps means that Mercury joins Earth as a tectonically active planet with new faults likely forming today as Mercury's interior continues to cool and the planet contracts," Tom Watters, Smithsonian senior scientist at the National Air and Space Museum in Washington, D.C., said in a statement . Mercury is the second densest planet after Earth, with a huge metallic core roughly 2,200 to 2,400 miles (3,600 to 3,800 km) wide, or about 75 percent of the planet's diameter. In comparison, Mercury's outer shell is only 300 to 400 miles (500 to 600 km) thick. The combination of its massive core and abundance of volatile elements has left scientists puzzled for years. A completely unexpected discovery Mariner 10 made was that Mercury possessed a magnetic field. Planets theoretically generate magnetic fields only if they spin quickly and possess a molten core. But Mercury takes 59 days to rotate and is so small — just roughly one-third Earth's size — that its core should have cooled off long ago.

"We had figured out how the Earth works, and Mercury is another terrestrial, rocky planet with an iron core, so we thought it would work the same way," Christopher Russell, a professor at the University of California, Los Angeles, said in a statement . An unusual interior could help to explain the differences in Mercury's magnetic field when compared to Earth. Observations from MESSENGER revealed that the planet's magnetic field is approximately three times stronger at its northern hemisphere than at its southern. Russell co-authored a model that suggests that Mercury's iron core may be turning from liquid to solid at the core's outer boundary rather than the inner. "It's like a snow storm in which the snow formed at the top of the cloud and middle of the cloud and the bottom of the cloud too," said Russell. "Our study of Mercury's magnetic field indicates iron is snowing throughout this fluid that is powering Mercury's magnetic field." The discovery in 2007 by Earth-based radar observations that Mercury's core may still be molten could help explain its magnetism, though the solar wind may play a role in dampening the planet's magnetic field. Although Mercury's magnetic field is just 1 percent the strength of Earth's, it is very active.

The magnetic field in the solar wind — the charged particles streaming off the sun — periodically touches upon Mercury's field, creating powerful magnetic tornadoes that channel the fast, hot plasma of the solar wind down to the planet's surface. Instead of a substantial atmosphere, Mercury possesses an ultra-thin "exosphere" made up of atoms blasted off its surface by solar radiation, the solar wind and micrometeoroid impacts. These quickly escape into space, forming a tail of particles. Mercury's orbital characteristics Mercury speeds around the sun every 88 Earth days, traveling through space at nearly 112,000 mph (180,000 km/h), faster than any other planet. Its oval-shaped orbit is highly elliptical, taking Mercury as close as 29 million miles (47 million km) and as far as 43 million miles (70 million km) from the sun. If one could stand on Mercury when it is nearest to the sun, it would appear more than three times as large as it does when viewed from Earth.

Oddly, due to Mercury's highly elliptical orbit and the 59 Earth-days or so it takes to rotate on its axis, when on the scorching surface of the planet, the sun appears to rise briefly, set, and rise again before it travels westward across the sky. At sunset, the sun appears to set, rise again briefly, and then set again. Mercury is the closest planet to the sun and has a thin atmosphere, no air pressure and an extremely high temperature. Take a look inside the planet. Credit: Karl Tate, SPACE.com Order of the Planets From The Sun – Planet Closest Distance to the Sun – PlanetFacts.org The Moon Order of the Planets From The Sun The solar system is a group of celestial bodies orbiting around the dwarf star called the Sun. The main members of the solar system are eight major planets, and their satellites. Other interesting members are comets, meteors and meteorites and dwarf planets. The order of the planets from the Sun from nearest to the farthest is Mercury, Venus, earth, Mars, Jupiter, Saturn Uranus, and Neptune. 1. The nearest planet to the Sun is Mercury.

Though it is very near to the Sun, it is not the hottest planet at all. The smallest among the inner planets has actually temperature of 450 degrees Celsius during day time while it drops to a very frigid negative 170 degrees Celsius at night. It is named after the Roman messenger of the Gods as it orbits the Sun once every 88 days. 2. The second planet from the Sun is named after the Roman Goddess of Beauty, Venus. True to its name, this beautiful planet is also called the evening star. It is also the hottest planet in the solar system due to clouds of toxic gas with temperatures over 460 degrees Celsius. It rotates backward and makes one complete revolution around the Sun in 225 days. 3. The third planet from the Sun is Earth, the beautiful blue planet blessed with a diversity of living organisms of varying shapes and sizes. It is the only planet known to sustain life. It makes a complete revolution around the Sun for 365 days. It has one satellite called the Moon. 4. Mars is the fourth planet from the Sun. It is named after the Roman God of War. It is usually called the red planet.

A Martian year is equivalent to 687 Earth days. It is usually the third brightest object of the night sky after Earth’s moon and Venus. The possibility of life on Mars is still a subject of probes and studies. By the way, Mars has similar seasons as here on Earth. 5. The biggest planet, Jupiter is the fifth planet from the Sun. Although it has the greatest volume among the planets, it has the lowest density. It is separated from the inner planets by the asteroid belt where many other interesting heavenly bodies orbit around the Sun. 6. Saturn is the second of the outer planets and is the sixth in order from the Sun. Many astronomers tag it as the most beautiful planet because of its prominent rings made up of ice, dust, gas, and other particles. 7. Uranus is the third of the outer planets, the seventh in order from the Sun. This planet has a very low density and is made up of a large proportion of gas. It is also referred to as an ice giant because a decent percentage of its gases are trapped in ice form. It has faint rings. 8. Neptune is the fourth among the outer planets and the farthest planet away from the Sun.

It is also made up of frozen gases like its neighboring planet Uranus. A great percentage of these gases are methane making it appear as a blue planet. What was once recognized as the ninth solar planet, Pluto, was just recently reclassified as a dwarf planet. It was placed in this category along with Eris, Vespa, and Ceres. Awesomeninja 18hunter235 Solar System Planets: Order of the 8 (or 9) Planets Solar System Planets: Order of the 8 (or 9) Planets By Robert Roy Britt | January 22, 2016 12:35pm ET MORE The planets of the solar system as depicted by a NASA computer illustration. Orbits and sizes are not shown to scale. Credit: NASA Ever since the discovery of Pluto in 1930, kids grew up learning about the nine planets of our solar system. That all changed starting in the late 1990s, when astronomers began to argue about whether Pluto was a planet.

In a highly controversial decision , the International Astronomical Union ultimately decided in 2006 to call Pluto a “dwarf planet,” reducing the list of “real planets” in our solar system to eight. However, astronomers are now hunting for another planet in our solar system, a true ninth planet , after evidence of its existence was unveiled on Jan. 20, 2016. The so-called "Planet Nine," as scientists are calling it, is about 10 times the mass of Earth and 5,000 times the mass of Pluto. [ Solar System Pictures: A Photo Tour ] If you insist on including Pluto , then that world would come after Neptune on the list; Pluto is truly way out there, and on a wildly tilted, elliptical orbit (two of the several reasons it got demoted). Interestingly, Pluto used to be the eighth planet, actually. More on that below. Terrestrial planets The inner four worlds are called “ terrestrial planets ,” because, like Earth, their surfaces are all rocky. Pluto, too, has a solid surface (and a very frozen one) but has never been grouped with the four terrestrials.

Jovian planets The four large outer worlds — Jupiter, Saturn, Uranus, and Neptune — are known as the “Jovian planets” (meaning “Jupiter-like”) because they are all huge compared to the terrestrial planets, and because they are gaseous in nature rather than having rocky surfaces (though some or all of them may have solid cores, astronomers say). According to NASA , "two of the outer planets beyond the orbit of Mars — Jupiter and Saturn — are known as gas giants; the more distant Uranus and Neptune are called ice giants." This is because, while the first two are dominated by gas, while the last two have more ice. All four contain mostly hydrogen and helium. Dwarf planets The IAU definition of a full-fledged planet goes like this: A body that circles the sun without being some other object's satellite, is large enough to be rounded by its own gravity (but not so big that it begins to undergo nuclear fusion, like a star) and has "cleared its neighborhood" of most other orbiting bodies. Yeah, that’s a mouthful.

The problem for Pluto, besides its small size and offbeat orbit, is that it shares its space with lots of other objects in the Kuiper Belt , beyond Neptune. Still, the demotion of Pluto remains controversial . The IAU planet definition puts other small, round worlds in the dwarf planet category, including the Kuiper Belt objects Eris , Haumea , and Makemake . Also now a dwarf planet is Ceres , a round object in the Asteroid Belt between Mars and Jupiter. Ceres was actually considered a planet when discovered in 1801 and then later deemed to be an asteroid. Some astronomers like to consider Ceres as a 10th planet (not to be confused with Nibiru or Planet X ), but that line of thinking opens up the possibility of there being 13 planets, with more bound to be discovered. The planets Below is a brief overview of the eight primary planets in our solar system , in order from the inner solar system outward: Mercury The closest planet to the sun, Mercury is only a bit larger than Earth's moon.

Its day side is scorched by the sun and can reach 840 degrees Fahrenheit (450 Celsius), but on the night side, temperatures drop to hundreds of degrees below freezing. Mercury has virtually no atmosphere to absorb meteor impacts, so its surface is pockmarked with craters, just like the moon. Over its four-year mission, NASA's MESSENGER spacecraft has revealed views of the planet that have challenged astronomers' expectations. Discovery: Known to the ancients and visible to the naked eye Named for: Messenger of the Roman gods Diameter: 3,031 miles (4,878 km) Orbit: 88 Earth days Venus' southern hemisphere, as seen in the ultraviolet. Credit: ESA Venus The second planet from the sun, Venus is terribly hot, even hotter than Mercury. The atmosphere is toxic. The pressure at the surface would crush and kill you. Scientists describe Venus’ situation as a runaway greenhouse effect. Its size and structure are similar to Earth, Venus' thick, toxic atmosphere traps heat in a runaway "greenhouse effect." Oddly, Venus spins slowly in the opposite direction of most planets. The Greeks believed Venus was two different objects — one in the morning sky and another in the evening.

Because it is often brighter than any other object in the sky — except for the sun and moon — Venus has generated many UFO reports. Discovery: Known to the ancients and visible to the naked eye Named for: Roman goddess of love and beauty Diameter: 7,521 miles (12,104 km) Orbit: 225 Earth days An image of the Earth taken by the Russian weather satellite Elektro-L No.1. Credit: NTsOMZ Earth The third planet from the sun, Earth is a waterworld, with two-thirds of the planet covered by ocean. It’s the only world known to harbor life. Earth’s atmosphere is rich in life-sustaining nitrogen and oxygen. Earth's surface rotates about its axis at 1,532 feet per second (467 meters per second) — slightly more than 1,000 mph (1,600 kph) — at the equator. The planet zips around the sun at more than 18 miles per second (29 km per second).

Diameter: 7,926 miles (12,760 km) Orbit: 365.24 days Day: 23 hours, 56 minutes Related: Mars researchers are focusing both Earth-based and planet orbiting sensors to better understand sources of methane on the red planet. Image Credit: Space Telescope Science Institute Mars The fourth planet from the sun, is a cold, dusty place. The dust, an iron oxide, gives the planet its reddish cast. Mars shares similarities with Earth: It is rocky, has mountains and valleys, and storm systems ranging from localized tornado-like dust devils to planet-engulfing dust storms. It snows on Mars. And Mars harbors water ice. Scientists think it was once wet and warm, though today it’s cold and desert-like. Mars' atmosphere is too thin for liquid water to exist on the surface for any length of time. Scientists think ancient Mars would have had the conditions to support life, and there is hope that signs of past life — possibly even present biology — may exist on the Red Planet.

Discovery: Known to the ancients and visible to the naked eye Named for: Roman god of war Diameter: 4,217 miles (6,787 km) Orbit: 687 Earth days Day: Just more than one Earth day (24 hours, 37 minutes) Related: Close-up of Jupiter's Great Red Spot as seen by a Voyager spacecraft. Credit: NASA/JPL-Caltech Jupiter The fifth planet from the sun, Jupiter is huge and is the most massive planet in our solar system. It’s a mostly gaseous world, mostly hydrogen and helium. Its swirling clouds are colorful due to different types of trace gases. A big feature is the Great Red Spot, a giant storm which has raged for hundreds of years. Jupiter has a strong magnetic field, and with dozens of moons, it looks a bit like a miniature solar system.

Discovery: Known to the ancients and visible to the naked eye Named for: Ruler of the Roman gods Diameter: 86,881 miles (139,822 km) Orbit: 11.9 Earth years The shadow of Saturn's moon Mimas dips onto the planet's rings and straddles the Cassini Division in this natural color image taken as Saturn approaches its August 2009 equinox. Credit: NASA/JPL/Space Science Institute Saturn The sixth planet from the sun is known most for its rings . When Galileo Galilei first studied Saturn in the early 1600s, he thought it was an object with three parts. Not knowing he was seeing a planet with rings, the stumped astronomer entered a small drawing — a symbol with one large circle and two smaller ones — in his notebook, as a noun in a sentence describing his discovery. More than 40 years later, Christiaan Huygens proposed that they were rings. The rings are made of ice and rock. Scientists are not yet sure how they formed. The gaseous planet is mostly hydrogen and helium. It has numerous moons .

Discovery: Known to the ancients and visible to the naked eye Named for: Roman god of agriculture Diameter: 74,900 miles (120,500 km) Orbit: 29.5 Earth years Day: About 10.5 Earth hours Related: Near-infrared views of Uranus reveal its otherwise faint ring system, highlighting the extent to which the planet is tilted. Credit: Lawrence Sromovsky, (Univ. Wisconsin-Madison), Keck Observatory Uranus The seventh planet from the sun, Uranus is an oddball. It’s the only giant planet whose equator is nearly at right angles to its orbit — it basically orbits on its side. Astronomers think the planet collided with some other planet-size object long ago, causing the tilt. The tilt causes extreme seasons that last 20-plus years, and the sun beats down on one pole or the other for 84 Earth-years. Uranus is about the same size as Neptune. Methane in the atmosphere gives Uranus its blue-green tint. It has numerous moons and faint rings.

Discovery: 1781 by William Herschel (was thought previously to be a star) Named for: Personification of heaven in ancient myth Diameter: 31,763 miles (51,120 km) Orbit: 84 Earth years Neptune’s winds travel at more than 1,500 mph, and are the fastest planetary winds in the solar system. Credit: NASA/JPL Neptune The eighth planet from the sun, Neptune is known for strong winds — sometimes faster than the speed of sound. Neptune is far out and cold. The planet is more than 30 times as far from the sun as Earth. It has a rocky core. Neptune was the first planet to be predicted to exist by using math, before it was detected. Irregularities in the orbit of Uranus led French astronomer Alexis Bouvard to suggest some other might be exerting a gravitational tug. German astronomer Johann Galle used calculations to help find Neptune in a telescope. Neptune is about 17 times as massive as Earth. Discovery: 1846 Pluto and its moons orbit the sun near the edge of our solar system.

Learn all about Pluto's weirdly eccentric orbit, four moons and more in this Space.com infographic . Credit: SPACE.com/Karl Tate Pluto (Dwarf Planet) Once the ninth planet from the sun, Pluto is unlike other planets in many respects. It is smaller than Earth's moon. Its orbit carries it inside the orbit of Neptune and then way out beyond that orbit. From 1979 until early 1999, Pluto had actually been the eighth planet from the sun. Then, on Feb. 11, 1999, it crossed Neptune's path and once again became the solar system's most distant planet — until it was demoted to dwarf planet status. Pluto will stay beyond Neptune for 228 years. Pluto’s orbit is tilted to the main plane of the solar system — where the other planets orbit — by 17.1 degrees. It’s a cold, rocky world with only a very ephemeral atmosphere. NASA's New Horizons mission performed history's first flyby of the Pluto system on July 14, 2015.

[Related: New Horizons' Pluto Flyby: Latest News, Images and Video ] Discovery: 1930 by Clyde Tombaugh Named for: Roman god of the underworld, Hades Diameter: 1,430 miles (2,301 km) Orbit: 248 Earth years NASA Solar System Exploration: Dwarf Planets Planet Nine Planet Nine orbits the sun at a distance that is 20 times farther out than the orbit of Neptune. (The orbit of Neptune is 2.7 billion miles from the sun at its closest point.) The strange world's orbit is about 600 times farther from the sun than the Earth's orbit is from the star. Scientists have not actually seen Planet Nine directly . Its existence was inferred by its gravitational effects on other objects in the Kuiper Belt, a region at the fringe of the solar system that is home to icy objects left over from the birth of the sun and planets. Closest Encounter with Jupiter until 2022 | Science Mission Directorate Closest Encounter with Jupiter until 2022 Join Mailing List Sept. 15, 2010: Been outside at midnight lately? There's something you really need to see.

Jupiter is approaching Earth for the closest encounter between the two planets in more than a decade--and it is dazzling. The night of closest approach is Sept. 20-21st. This is also called "the night of opposition" because Jupiter will be opposite the sun, rising at sunset and soaring overhead at midnight. Among all denizens of the midnight sky, only the Moon itself will be brighter. Science@NASA reader Tamas Ladanyi took this picture of a friend photographing Jupiter over a lake in the Bakony mountains of Hungary on Sept. 5th. "The giant planet was remarkably bright," says Ladanyi. [ larger image ] Earth-Jupiter encounters happen every 13 months when the Earth laps Jupiter in their race around the sun. But because Earth and Jupiter do not orbit the sun in perfect circles, they are not always the same distance apart when Earth passes by. On Sept. 20th, Jupiter will be as much as 75 million km closer than previous encounters and will not be this close again until 2022. The view through a telescope is excellent. Because Jupiter is so close, the planet's disk can be seen in rare detail--and there is a lot to see.

For instance, the Great Red Spot, a cyclone twice as wide as Earth, is bumping up against another storm called "Red Spot Jr." The apparition of two planet-sized tempests grinding against one another must be seen to be believed. Jupiter's "kissing red spots" photographed by Alan Friedman of Buffalo, NY, using a 10-inch telescope. The full-sized image shows the golden disk of Jupiter's moon Io. Also, Jupiter's trademark South Equatorial Belt (SEB) recently vanished , possibly submerging itself beneath high clouds. Researchers say it could reappear at any moment. The dramatic resurgence would be accompanied by a globe-straddling profusion of spots and cloudy swirls, clearly visible in backyard telescopes. And what was that flash? Amateur astronomers have recently reported a surprising number of fireballs in Jupiter's atmosphere. Apparently, many small asteroids or comet fragments are hitting the giant planet and exploding among the clouds. Researchers who have studied these events say visible flashes could be occurring as often as a few times a month. Finally, we mustn't forget the moons of Jupiter because they are also having a close encounter with Earth.

These are planet-sized worlds with active volcanoes (Io), possible underground oceans (Europa), vast fields of craters (Callisto), and mysterious global grooves (Ganymede). When Galileo discovered the moons 400 years ago, they were no more than pinpricks of light in his primitive spy glass. Big, modern amateur telescopes reveal actual planetary disks with colorful markings. It makes you wonder, what would Galileo think? Answer: "I'm getting up at midnight!" What is the Closest Planet to Earth? - Universe Today Universe Today What is the Closest Planet to Earth? Article Updated: 23 Dec , 2016 by Matt Williams A common question when looking at the Solar System and Earth’s place in the grand scheme of it is “which planet is closest to Earth?” Aside from satisfying a person’s general curiosity, this question is also of great importance when it comes to space exploration. And as humanity contemplates mounting manned missions to neighboring planets, it also becomes one of immense practicality. If, someday, we hope to explore, settle, and colonize other worlds, which would make for the shortest trip? Invariable, the answer is Venus .

Often referred to as “ Earth’s Twin “, Venus has many similarities to Earth. It is a terrestrial planet, it orbits within the Sun’s habitable zone, and it has an atmosphere that is believed to have once been like Earth’s. Combined with its proximity to us, its little wonder we consider it our twin. Venus’ Orbit: Venus orbits the Sun at an average distance (semi-major axis) of 108,208,000 km (0.723 AUs), ranging between 107,477,000 km (0.718 AU) at perihelion and 108,939,000 km (0.728 AU) at aphelion. This makes Venus’ orbit the least eccentric of all the planets in the Solar System. In fact, with an eccentricity of less than 0.01, its orbit is almost circular. Earth and Venus’ orbit compared. Credit: Sky and Telescope When Venus lies between Earth and the Sun, it experiences what is known as an inferior conjunction.

It is at this point that it makes its closest approach to Earth (and that of any planet) with an average distance of 41 million km (25,476,219 mi). On average, Venus achieves an inferior conjunction with Earth every 584 days. And because of the decreasing eccentricity of Earth’s orbit, the minimum distances will become greater over the next tens of thousands of years. So not only is it Earth’s closest neighbor (when it makes its closest approach), but it will continue to get cozier with us as time goes on! Venus vs. Mars: As Earth’s other neighbor, Mars also has a “close” relationship with Earth. Orbiting our Sun at an average distance of 227,939,200 km (1.52 AU), Mars’ highly eccentric orbit (0.0934) takes it from a distance of 206,700,000 km (1.38 AU) at perihelion to 249,200,000 km (1.666 AU) at aphelion.

This makes its orbit one of the more eccentric in our Solar System, second only to Mercury For Earth and Mars to be at their closest, both planets needs to be on the same side of the Sun, Mars needs to be at its closest distance from the Sun (perihelion), and Earth needs to be at its farthest (aphelion). This is known as opposition, a time when Mars appears as one of the brightest objects in the sky (as a red star), rivaling that of Venus or Jupiter. The eccentricity in Mars’ orbit means that it is . Credit: NASA But even at this point, the distance between Mars and Earth ranges considerably. The closest approach to take place occurred back in 2003, when Earth and Mars were only 56 million km (3,4796,787 mi) apart. And this was the closest they’d been in 50,000 years. The next closest approach will take place on July 27th, 20178, when Earth and Mars will be at a distance of 57.6 million km (35.8 mi) from each other.

It has also been estimated that the closest theoretical approach would take place at a distance of 54.6 million km (33.9 million mi). However, no such approach has been documented in all of recorded history. One would be forced to wonder then why so much of humanity’s exploration efforts (past, present and future) are aimed at Mars. But when one considers just how horrible Venus’ environment is in comparison, the answer becomes clear. Exploration Efforts: The study and exploration of Venus has been difficult over the years, owing to the combination of its dense atmosphere and harsh surface environment. Its surface has been imaged only in recent history, thanks to the development of radar imaging. However, many robotic spacecraft and even a few landers have made the journey and discovered much about Earth’s closest neighbor. The first attempts were made by the Soviets in the 1960s through the Venera Program . Whereas the first mission ( Venera-1 ) failed due to loss of contact, the second ( Venera-3 ) became the first man-made object to enter the atmosphere and strike the surface of another planet (on March 1st, 1966).

This was followed by the Venera-4 spacecraft, which launched on June 12th, 1967, and reached the planet roughly four months later (on October 18th). The first color pictures taken of the surface of Venus by the Venera-13 space probe. Credit: NASA NASA conducted similar missions under the Mariner program. The Mariner 2 mission, which launched on December 14th, 1962, became the first successful interplanetary mission and passed within 34,833 km (21,644 mi) of Venus’ surface. Between the late 60s and mid 70s, NASA conducted several more flybys using Mariner probes – such as the Mariner 5 mission on Oct. 19th, 1967 and the Mariner 10 mission on Feb. 5th, 1974. The Soviets launched six more Venera probes between the late 60s and 1975, and four additional missions between the late 70s and early 80s.

Venera-5 , Venera-6 , and Venera-7 all entered Venus’ atmosphere and returned critical data to Earth. Venera 11 and Venera 12 detected Venusian electrical storms; and Venera 13 and Venera 14 landed on the planet and took the first color photographs of the surface. The program came to a close in October 1983, when Venera 15 and Venera 16 were placed in orbit to conduct mapping of the Venusian terrain with synthetic aperture radar. By the late seventies, NASA commenced the Pioneer Venus Project , which consisted of two separate missions. The first was the Pioneer Venus Orbiter , which inserted into an elliptical orbit around Venus (Dec. 4th, 1978) to study its atmosphere and map the surface. The second, the Pioneer Venus Multiprobe , released four probes which entered the atmosphere on Dec. 9th, 1978, returning data on its composition, winds and heat fluxes. Artist’s impression of NASA’s Pioneer Venus Orbiter in orbit around Venus.

Credit: NASA In 1985, the Soviets participated in a collaborative venture with several European states to launch the Vega Program . This two-spacecraft initiative was intended to take advantage of the appearance of Halley’s Comet in the inner Solar System, and combine a mission to it with a flyby of Venus. While en route to Halley on June 11th and 15th, the two Vega spacecraft dropped Venera-style probes into Venus’ atmosphere to map its weather. NASA’s Magellan spacecraft was launched on May 4th, 1989, with a mission to map the surface of Venus with radar. In the course of its four and a half year mission, Magellan provided the most high-resolution images to date of the planet, was able to map 98% of the surface and 95% of its gravity field. In 1994, at the end of its mission, Magellan was sent to its destruction into the atmosphere of Venus to quantify its density. Venus was observed by the Galileo and Cassini spacecraft during flybys on their respective missions to the outer planets, but Magellan was the last dedicated mission to Venus for over a decade.

It was not until October of 2006 and June of 2007 that the MESSENGER probe would conduct a flyby of Venus (and collect data) in order to slow its trajectory for an eventual orbital insertion of Mercury. The Venus Express , a probe designed and built by the European Space Agency, successfully assumed polar orbit around Venus on April 11th, 2006. This probe conducted a detailed study of the Venusian atmosphere and clouds, and discovered an ozone layer and a swirling double-vortex at the south pole before concluding its mission in December of 2014 . Since December 7th, 2015, Japan’s Akatsuki has been in a highly elliptical Venusian orbit. Because of its hostile surface and atmospheric conditions, Venus has proven to be a tough nut to crack, despite its proximity to Earth. In spite of that, NASA, Roscosmos, and India’s ISRO all have plans for sending additional missions to Venus in the coming years to learn more about our twin planet. And as the century progresses, and if certain people get their way, we may even attempt to send human colonists there !

If you’d like more info on Earth, check out NASA’s Solar System Exploration Guide on Earth . And here’s a link to NASA’s Earth Observatory . Astronomy Cast also has an interesting episode on the subject. Listen here, Episode 50: Venus . Share this: If Venus once had an atmosphere similar to Earth, what happened? I understand the average temperature on Venus now exceeds a uniform 900 degrees Fahrenheit over the entire planet! Helio George Earth Is Closest to the Sun for 2013 Today Earth Is Closest to the Sun for 2013 Today Geoff Gaherty Pin it Share The orbits of the four inner planets: Mercury, Venus, Earth, and Mars. On Jan. 2, 2013, the Earth is at perihelion, its closest point to the sun of the year. More If the sun looks a little larger than usual today, you're not seeing things. Today (Jan. 2) marks the time when the Earth is at perihelion, the point in its orbit at which it is closest to the sun.

During perihelion, the Earth is exactly 91,402,560 miles (147,098,161 kilometers) from the sun.In actuality, you most likely can't see any difference between the apparent size of the sun today and its appearance at aphelion (when the Earth will be farthest from the star).The difference is only 3.4 percent, too small to be detected with the naked eye. On average, the Earth is about 93 million miles (150 million km) from the sun. It will be farthest from the sun on July 5, when the Earth reaches aphelion, a point 94,508,960 miles (152,097,427 km) from the sun. The closest and farthest differences from the sun are very similar because the Earth’s orbit is very close to being circular. In fact, as planetary orbits go, ours is close to perfect. The eccentric Earth Only Venus and Neptune have more circular orbits than the Earth.

On the other hand, if you look at the diagram of the orbits of the four inner planets accompanying this story, you may easily see that Mercury and Mars have orbits which are seriously eccentric. Astronomers use the term "eccentric" in its original mathematical sense, meaning "away from the center." A perfect circle has an eccentricity of 0. A straight line would have an eccentricity of 1. Everything else in between is an oval of some kind. Here's a look at the innermost planets of the solar system in order of increasing eccentricity: Venus: 0.006785 Mars: 0.093277 Mercury: 0.205649 Looking at the diagram, the orbits of Earth and Venus look almost perfectly circular, while that of Mars is slightly closer to the sun towards the bottom. Mercury's orbit is very much closer to the sun on the right. If you look closely, there is a little tick mark on the orbits to indicate where perihelion lies. Don't confuse this mark with the little wedges which denote the orbital nodes, the points where the orbits cross the plane of the ecliptic.

The Earth appears right next to the tick mark on its orbit marking perihelion in the image. Closer to the sun So what is the difference for the inhabitants of Earth when our planet is at perihelion instead of aphelion? The Earth is slightly warmer than it would be otherwise, about 4 degrees Fahrenheit (2.3 degrees Celsius). [ Earth Quiz: How Well Do You Know Our Planet? ] This perihelion effect is very minor compared to the effects of the tilt of our planet's axis. During December in the Northern Hemisphere, the North Pole is tilted away from the sun so that we receive less sunlight every day. At the same time, the South Pole is tilted towards the sun, so the Southern Hemisphere receives more sun and experiences summer. In June, the situation is reversed and we have summer in the northern hemisphere and winter in the southern hemisphere. The only effect of perihelion is that the winters in the Northern Hemisphere are very slightly milder than the winters in the southern hemisphere at the equivalent latitudes. Not as many people live as close to the South Pole as do close to the North Pole, so humanity isn't affected much.

So enjoy that "big" January sun, and look forward to the longer days to come as Earth moves around its orbit to the point where we really receive more sun and spring arrives. This article was provided to SPACE.com by Starry Night Education , the leader in space science curriculum solutions. Follow Starry Night on Twitter @StarryNightEdu . Earth closest to sun on January 4 | Tonight | EarthSky Earth closest to sun on January 4 By Bruce McClure in Tonight | January 4, 2017 Source: Fred Espenak’s Earth at perihelion and aphelion, 2001 to 2100 The word perihelion is from Greek roots peri meaning near, and helios meaning sun. Earth is closest to the sun every year in early January, when it’s winter for the Northern Hemisphere. We’re farthest away from the sun in early July, during our Northern Hemisphere summer. Earth is about 3 million miles (5 million km) closer to the sun in early January than it is in early July. That’s not a huge change in distance. It’s not enough of a change to cause the seasons on Earth.

On January 4, 2017, Earth at its closest point swings to within 91,404,322 miles (147,100,993 km) of the sun. That’s in contrast to six months from now, when the Earth reaches aphelion – its most distant point – on July 3, 2017. Then we’ll be 94,505,901 miles (152,092,511 km) from the sun. Image credit: NASA So you see there’s not a huge amount of difference between perihelion and aphelion. Earth’s orbit is very nearly circular. It’s not our distance from the sun, but the tilt of our world’s axis that creates winter and summer. In winter, your part of Earth is tilted away from the sun. In summer, your part of Earth is tilted toward the sun. The day of maximum tilt toward or away from the sun is the December or June solstice. Though not responsible for the seasons, Earth’s closest and farthest points to the sun do affect seasonal lengths.

When the Earth comes closest to the sun for the year, as around now, our world is moving fastest in orbit around the sun. Earth is rushing along now at almost 19 miles per second (30.3 km/ sec) – moving about a kilometer per second faster than when Earth is farthest from the sun in early July. Thus the Northern Hemisphere winter and – simultaneously – Southern Hemisphere summer are the shortest seasons as Earth rushes from the solstice in December to the equinox in March. In the Northern Hemisphere, the summer season (June solstice to September equinox) lasts nearly 5 days longer than our winter season. And, of course, the corresponding seasons in the Southern Hemisphere are opposite. Southern Hemisphere winter is nearly 5 days longer than Southern Hemisphere summer. It’s all due to the shape of Earth’s orbit. The shape is an ellipse, like a circle someone sat down on and squashed. The elliptical shape of Earth’s orbit causes the variation in the length of the seasons – and brings us closest to the sun in January.

Image Credit: Dna-webmaster Bottom line: In 2017, Earth’s closest point to the sun – called its perihelion – comes on January 4 at 14:18 Universal Time (8:18 a.m. CST). Mercury Home to Ice, Messenger Spacecraft Findings Suggest - The New York Times The New York Times Space & Cosmos |On Closest Planet to the Sun, NASA Finds Lots of Ice Search Continue reading the main story Photo Deep within craters near Mercury’s poles, temperatures dip to as low as 370 degrees below zero. Credit NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington Mercury is as cold as ice. Indeed, Mercury, the closest planet to the Sun , possesses a lot of ice — 100 billion to one trillion tons — scientists working with NASA’s Messenger spacecraft reported on Thursday. Sean C. Solomon, the principal investigator for Messenger, said there was enough ice there to encase Washington, D.C., in a frozen block two and a half miles deep. That is a counterintuitive discovery for a place that also ranks among the hottest in the solar system.

At noon at the equator on Mercury, the temperature can hit 800 degrees Fahrenheit. But near Mercury’s poles, deep within craters where the Sun never shines, temperatures dip to as cold as minus 370. “In these planetary bodies, there are hidden places, as it were, that can have interesting things going on,” said David J. Lawrence, a senior scientist at the Johns Hopkins University Applied Physics Laboratory working on the Messenger mission. Advertisement Continue reading the main story The findings appear in a set of three papers published Thursday on the Web site of the journal Science . The ice could be an intriguing science target for a future robotic lander or even a resource for astronauts in the far future. Planetary scientists had strong hints of the ice a couple of decades ago when telescopes bounced radio waves off Mercury and the reflections were surprisingly bright. But some researchers suggested the craters could be lined with silicate compounds or sulfur, which might also be highly reflective. The Messenger spacecraft, which swung into orbit around Mercury in March 2011 and has completed its primary mission, took a closer look by counting particles known as neutrons that are flying off the planet. High-energy cosmic rays break apart atoms, and the debris includes neutrons.

But when a speeding neutron hits a hydrogen atom, which is almost the same weight, it comes to almost a complete stop, just as the cue ball in billiards transfers its momentum when it hits another ball. Water molecules contain two hydrogen atoms, and thus when Messenger passed over ice-rich areas, the number of neutrons dropped. Please verify you're not a robot by clicking the box. Invalid email address. Please re-enter. You must select a newsletter to subscribe to. Sign Up The same technique was used to detect frozen water below the surface on Mars and within similar craters on the Moon . The neutron number would not have dropped if the bright surfaces had been made of sulfur or silicates. “Water ice is the only candidate we’ve got that fits all those observations,” said Dr. Solomon, who is also director of Columbia’s Lamont-Doherty Earth Observatory. The ice is almost pure water, which indicates that it arrived within the last few tens of millions of years, possibly from a comet that smacked into Mercury. Dr. Solomon said several young craters on the surface of Mercury could be candidates for such an impact. Not all of the icy regions were bright.

In slightly warmer regions, where temperatures exceed minus 280, the ice was covered by a dark layer about half a foot thick. The scientists believe in these places the water ice vaporized, leaving behind other materials that had been trapped, including carbon-based molecules known as organics. Advertisement Continue reading the main story That could be similar to how water and the building blocks of life reached Earth billions of years ago. The water could also be an intriguing resource for people. Between the scorched equator and the frozen poles, temperatures on Mercury can be temperate, especially a few feet below the surface, where the soil insulates against the temperature swings between day and night — an ideal location to build a colony. “People joke about it, but it’s not so crazy, really,” said David A. Paige, a professor of geology at U.C.L.A. who calculated the crater temperatures. A version of this article appears in print on November 30, 2012, on Page A3 of the New York edition with the headline: On Planet Closest to Sun, NASA Finds Plenty of Ice.

Order Reprints | Today's Paper | Subscribe Planet Closest to the Sun - Universe Today Universe Today Planet Closest to the Sun Article Updated: 24 Dec , 2015 by Jerry Coffey [/caption]Mercury, the planet closest to the Sun, is a study in extremes and offers many surprises. The extremes of the planet have made it an understudied body in our Solar System, though the MESSENGER mission is trying to change that as you are reading this article. In addition to being the planet closest to the Sun, Mercury is also the smallest by mass. If you ignore the former planet Pluto, it is also the smallest by surface area, as well. The planet has the most eccentric orbit: at perihelion it is 46,001,200 km from the Sun and at aphelion it is 69,816,900 km. The planet’s short orbital period(87.969 Earth days) and slight axial tilt combine to make the day on Mercury(116 Earth days) longer than the year. The average temperature on the planet is 442.5°K.

Because of the planet’s thin atmosphere there is a wide temperature range, 100°K to 700°K. The temperature at the equator can be as much as 300°K more than the temperature at the poles. Despite its proximity to our central star, the poles of the planet are thought to have water ice hidden within impact craters. Claims for water ice are substantiated by observations by the 70 m Goldstone telescope and the Very Large Array. There are areas of very high radar reflection at the pole areas so, since water is highly reflective of radar, astronomers believe that water ice is the most likely cause of this reflection. Due to its size and average temperatures, the planet’s gravity can not retain a significant atmosphere over a long period. It does have a negligible surface-bounded exosphere that is dominated by hydrogen, helium, oxygen, sodium, calcium, and potassium. Atoms are continuously being lost and replenished from this exosphere. Hydrogen and helium atoms are thought to derive from the solar wind that buffets the planet. These elements diffuse into Mercury’s magnetosphere before escaping back into space. Radioactive decay within the crust is a source of helium, sodium, and potassium.

Mercury has been explored by two mission: Mariner 10 and MESSENGER. Mariner 10 was able to map 40-45% of Mercury’s surface through more than 2,800 photos. It revealed a more or less moon-like surface, a slight atmosphere, a magnetic field, and a large iron rich core. MESSENGER was launched in August of 2004. After a 31/2 year flight, it made its first flyby in January 2008 and arrived in orbit on March 18, 2011. So far, the probe has discovered large amounts of water in the exosphere, evidence of past volcanic activity, and evidence of a liquid planetary core. As the MESSENGER mission continues, the closest planet to the Sun should continue to reveal more surprises for the scientists at NASA. It appears a new age of discovery has begun for Mercury. We have an extensive section just on Mercury on Universe Today. And did you know there’s a spacecraft visiting Mercury called MESSENGER? You can read news about this mission here . Here’s a link to NASA’s Solar System Exploration Guide on Mercury.

We have recorded an episode of Astronomy Cast just about the Sun called The Sun, Spots and All . References: Mars Close Approaches | Mars Exploration Program Mars Close Approach to Earth: May 30, 2016 See Mars in the Night Sky! Simply go outside and look up, contact your local planetarium, or look for a star party near you. In 2016, the planet Mars will appear brightest from May 18 to June 3. Mars Close Approach is May 30, 2016. That is the point in Mars' orbit when it comes closest to Earth. Mars will be at a distance of 46.8 million miles (75.3 million kilometers). Mars reaches its highest point around midnight -- about 35 degrees above the southern horizon, or one third of the distance between the horizon and overhead. Mars will be visible for much of the night. By mid-June, Mars will become fainter as Mars and Earth travel farther away from each other in their orbits around the Sun. Miss seeing Mars Close Approach in 2016? The next Mars Close Approach is July 31, 2018.

You need a iFrames Capable browser to view this content. What's Up For May 2016 What can you see in the sky this month? Mercury transits the sun and Mars is closer to Earth than it has been in 11 years. Watch to learn how and where to look for them. In 2016, Mars will appear brightest from May 18-June 3. Its closest approach to Earth is May 30. That is the point in Mars' orbit when it comes closest to Earth. Mars will be at a distance of 46.8 million miles (75.3 million kilometers). Credit: NASA/JPL-Caltech Mars Close Approach What is Mars Close Approach? Close approach is when Mars and Earth come nearest to each other in their orbits around the sun. Close is a relative term. The minimum distance from the Earth to Mars is about 54.6 million kilometers. However, that doesn't happen very often. If Earth and Mars had perfectly circular orbits, their minimum distance would always be the same. However, they have elliptical (egg-shaped) paths. In addition, gravitational tugging by planets constantly changes the shape of their orbits a little bit.

Giant Jupiter especially influences the orbit of Mars. The orbits of Mars and Earth are also slightly tilted with respect to each other. All of these factors mean that not all close encounters are equal. In 2003 , Mars made its closest approach to Earth in nearly 60,000 years! It won't be that close again until the year 2287. When Mars and Earth are close to each other, Mars appears very bright in our sky. It also makes it easier to see with telescopes or the naked eye. The Red Planet comes close enough for exceptional viewing only once or twice every 15 or 17 years. Close Approach: Mars Hoax However, don't be fooled by the Mars Hoax! Since 2003 , this urban legend gets circulated through email and social media every time Mars makes a close approach. The message is that Mars will look as big as the Moon in our night sky. If that were true, we'd be in big trouble given the gravitational pulls on Earth, Mars, and our Moon! When does Mars Close Approach Occur? Mars Close Approach happens about every 26 months. It is closely related to Mars Opposition and Mars Retrograde .

Since Mars and Earth are at their closest, it's generally the best time to go to Mars. Many Mars missions have taken advantage of the close distance to visit the red planet. That's why, depending on budgets, you'll often see that Mars missions launch about every two years:

Question: Which is the closet planet to the sun to have a moon ?
Answer: Earth